How to get the size of a JavaScript object?

Question

I want to know the size occupied by a JavaScript object.

Take the following function:

function Marks(){
  this.maxMarks = 100;
}

function Student(){
  this.firstName = "firstName";
  this.lastName = "lastName";
  this.marks = new Marks();
}

Now I instantiate the student:

var stud = new Student();

so that I can do stuff like

stud.firstName = "new Firstname";

alert(stud.firstName);

stud.marks.maxMarks = 200;

etc.

Now, the stud object will occupy some size in memory. It has some data and more objects.

How do I find out how much memory the stud object occupies? Something like a sizeof() in JavaScript? It would be really awesome if I could find it out in a single function call like sizeof(stud).

I’ve been searching the Internet for months—couldn’t find it (asked in a couple of forums—no replies).

Answer 1

I have re-factored the code in my original answer. I have removed the recursion and removed the assumed existence overhead.

function roughSizeOfObject( object ) {

    var objectList = [];
    var stack = [ object ];
    var bytes = 0;

    while ( stack.length ) {
        var value = stack.pop();

        if ( typeof value === 'boolean' ) {
            bytes += 4;
        }
        else if ( typeof value === 'string' ) {
            bytes += value.length * 2;
        }
        else if ( typeof value === 'number' ) {
            bytes += 8;
        }
        else if
        (
            typeof value === 'object'
            && objectList.indexOf( value ) === -1
        )
        {
            objectList.push( value );

            for( var i in value ) {
                stack.push( value[ i ] );
            }
        }
    }
    return bytes;
}